NATIONAL GLASS MART
DISTRIBUTORS & WHOLESALERS
TOUGHENED GLASS
Toughened safety glass is ideal for bolted structural glazing and frameless applications. Superb resistance to thermal stress also allows toughened safety glass to be used in applications such as refrigerator and oven doors, where ordinary annealed glass would be likely to fracture. Toughened safety glass is available in a range of thicknesses and various colours. Toughened safety glass meets the safety glass requirements of the South African National Building Regulations. Toughened safety glass is up to 5 times stronger than normal monolithic float glass. Surface treatments – Toughened glass cannot be drilled or edgeworked in any manner. Sand blasting and other surface treatments should be carried out prior to toughening. Deep sand blasted patterns greater than 1mm are not permissible.
Templates – For toughened glass ordered to templates refer to our template processing guidelines.
Minimum edgework – Finish on toughened glass up to and including 8mm is standard arrised edge. Minimum edge work on greater thicknesses will be a flat ground edge.
Bowing – Slight distortion or bowing may occur after toughening but is largely controllable. It will vary with substance, tint, surface treatment, size and shape of the glass. Ceramic painted, sand blasted or reflective coated glass has a greater tendency to bow and special tolerances would be advised. Flatness will be measured when the glass is standing on edge with a straight edge placed along the full length of the panel and a wedge measurement taken at the centre position
Visual distortion – The furnacing of glass panels can produce slight corrugated distortion or roller waves. This visual effect is in the form of distortion bands 250–300mm apart. It is more noticeable in tinted and reflective toughened glass. It is recommended that the roller wave run horizontal on the glass subject to the sizing constraints of the toughening furnace. Less visual distortion is evident with a heat strengthened glass. Talk to our staff about specific optical requirements;
Quench pattern – During the quenching phase of the toughening process, the glass is rapidly cooled by high velocity blasts of air. Inevitably this results in slightly higher levels of compression at those areas adjacent to the air nozzles. The consequence of this is the occasional appearance of a strain pattern or iridescent spots or darkish shadows. This effect is referred to as the quench pattern as it occurs in the furnace quench. Typically, the pattern is only visible at times of polarised light (polarised sunglasses) or by viewing the glass from the inside at acute angles. Similarly, the thicker and more reflective the glass, the more obvious the pattern will be;
Plastic wrap on toughened glass is used to protect the glass during transport. The plastic wrap should be removed no later than one month after exposure to sunlight.
